The individual exposures were acquired using the standard PCWI
nod-and-shuffle technique, where the central 1/3 of the CCD is used
for recording the spectrum while masking the outer 2/3 of the CCD,
restricting the spectral bandpass to \(\sim \) 
150 Å [1]}. Note that our DLA
sample is preselected based on the likely presence of Ly\(\alpha \) 
emission within the 2 or 3 arcsec SDSS-III or SDSS-II fibre spectra.
Thus, it is expected that the DLA host galaxy lies at small impact
parameters (i.e, \(\sim \)  8 to 12 kpc). However, to trace the
large scale environment around the quasar, while performing
nod-and-shuffle, we offset the frame by 25 arcsec so that the
quasar remains within the frame at all time. We acquired a series
of 1200s exposures, totalling 1.6 h with the quasar at the center,
and 1.6 h after the offset. Combined, this technique doubles the
total integration time for the object, to 3.3 h. This strategy
resulted in an effective field of view of \(20\times 40\)  with the quasar at the center which allow us to search
for the DLA host galaxy and trace its large scale environment out
to \(\approx 80~\rm kpc\)  (\(\approx 10\)  arcsec at \(z \sim 3\) ).
